Action potentials recorded from bundles of very thin, gray matter axons in rat cerebellar slices using a grease-gap method

Palani, D.; Pekala, Dobromila; Baginskas, Armuntas; Szkudlarek, Hanna; Raastad, Morten

doi:10.1016/j.jneumeth.2012.05.005

Cited by 4 publications

(28 citation statements)

References 33 publications

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“…We repeated the parallel fiber stimulus four times with 20 msec intervals, which is within the duration of the DAP (Palani et al. ; Pekala et al. ) and within the range of granule cell firing frequencies in vivo (Eccles et al.…”

Section: Resultsmentioning

confidence: 99%

“…Because the initial segment of the axon has other membrane currents, axial resistance, and input resistance than more distal parts (Kole and Stuart ) which theoretically could influence our somatically recorded DAPs, we also recorded the waveform of the axonal spikes far away from the soma using a miniaturized grease‐gap method (Palani et al. ).…”

Section: Resultsmentioning

confidence: 99%

“…We therefore measured cAP amplitude from the parallel fibers using a grease‐gap method (Palani et al. ). Somatic membrane potential and grease‐gap recorded cAP will be influenced by axonal membrane potential and spike amplitude, respectively, although further qualifications will be given in the Discussion.…”

Section: Resultsmentioning

confidence: 99%

“…To monitor changes in the axonal action potential with its depolarizing after‐potential (DAP) during fever‐like temperatures, we used the grease‐gap technique as previously described (Palani et al. ; Pekala et al. ).…”

Section: Methodsmentioning

confidence: 99%

“…Interestingly, typical cortical thin axons and several peripheral thin axons have an intrinsic mechanism, the depolarizing after‐potential (DAP), that increases axonal excitability for 50–100 msec after a spike (Gardner‐Medwin ; Wigstrom and Gustafsson ; Palani et al. ), and may therefore reduce conduction failures.…”

Section: Introductionmentioning

confidence: 99%

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Typical gray matter axons in mammalian brain fail to conduct action potentials faithfully at fever-like temperatures

2016

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We studied the ability of typical unmyelinated cortical axons to conduct action potentials at fever‐like temperatures because fever often gives CNS symptoms. We investigated such axons in cerebellar and hippocampal slices from 10 to 25 days old rats at temperatures between 30 and 43°C. By recording with two electrodes along axonal pathways, we confirmed that the axons were able to initiate action potentials, but at temperatures >39°C, the propagation of the action potentials to a more distal recording site was reduced. This temperature‐sensitive conduction may be specific for the very thin unmyelinated axons because similar recordings from myelinated CNS axons did not show conduction failures. We found that the conduction fidelity improved with 1 mmol/L TEA in the bath, probably due to block of voltage‐sensitive potassium channels responsible for the fast repolarization of action potentials. Furthermore, by recording electrically activated antidromic action potentials from the soma of cerebellar granule cells, we showed that the axons failed less if they were triggered 10–30 msec after another action potential. This was because individual action potentials were followed by a depolarizing after‐potential, of constant amplitude and shape, which facilitated conduction of the following action potentials. The temperature‐sensitive conduction failures above, but not below, normal body temperature, and the failure‐reducing effect of the spike's depolarizing after‐potential, are two intrinsic mechanisms in normal gray matter axons that may help us understand how the hyperthermic brain functions.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Typical gray matter axons in mammalian brain fail to conduct action potentials faithfully at fever-like temperatures

2016

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Components of action potential repolarization in cerebellar parallel fibres

Pekala

Baginskas

Szkudlarek

et al. 2014

The Journal of Physiology

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Key pointsr The presynaptic action potential waveform was investigated in cerebellar parallel fibres from rats.r The spike repolarization was composed of a fast tetraethylammonium-sensitive component and a slow margatoxin-sensitive depolarized after-potential (DAP). These components could be manipulated relatively independently, possibly offering independent control of synchronous and asynchronous transmitter release.r Axonal electrical activation sometimes gave bursts of action potentials at the soma; these bursts were created by the axon because they invaded the soma at membrane potentials well below the somatic spike threshold.r Axonal bursts could reliably be induced by increasing the DAP pharmacologically, suggesting that proper control of DAP amplitude is necessary to suppress axonal bursting.r The fast repolarization was particularly well controlled because blockers of three groups of K + channels (tetraethylammonium, margatoxin and quinine) were needed to abolish it.Abstract Repolarization of the presynaptic action potential is essential for transmitter release, excitability and energy expenditure. Little is known about repolarization in thin, unmyelinated axons forming en passant synapses, which represent the most common type of axons in the mammalian brain's grey matter. We used rat cerebellar parallel fibres, an example of typical grey matter axons, to investigate the effects of K + channel blockers on repolarization. We show that repolarization is composed of a fast tetraethylammonium (TEA)-sensitive component, determining the width and amplitude of the spike, and a slow margatoxin (MgTX)-sensitive depolarized after-potential (DAP). These two components could be recorded at the granule cell soma as antidromic action potentials and from the axons with a newly developed miniaturized grease-gap method. A considerable proportion of fast repolarization remained in the presence of TEA, MgTX, or both. This residual was abolished by the addition of quinine. The importance of proper control of fast repolarization was demonstrated by somatic recordings of antidromic action potentials. In these experiments, the relatively broad K + channel blocker 4-aminopyridine reduced the fast repolarization, resulting in bursts of action potentials forming on top of the DAP. We conclude that repolarization of the action potential in parallel fibres is supported by at least three groups of K + channels. Differences in their temporal profiles allow relatively independent control of the spike and the DAP, whereas overlap of their temporal profiles provides robust control of axonal bursting properties.

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Analysis of the ENU-3 protein family in nervous system development in C. elegans

Florica¹

2023

Preprint

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During the development of the nervous system, neurons are guided to their final targets by several well-known guidance cues. In Caenorhabditis elegans the expression of the UNC-6/Netrin guidance cue along the ventral cord attracts axons that express UNC-40, while repulsing axons that express both the UNC-5 and UNC-40 receptors. Lack of both UNC-40 and the novel protein ENU-3 enhanced the ventral guidance defects of the AVM and PVM (Yee et al., 2014). This suggests that ENU-3 functions in an UNC-6 dependent pathway parallel to UNC-40 in controlling migrations towards the ventral nerve cord. Mutations in all proteins of the ENU-3 family also enhance the motor neuron axon outgrowth defects of strains lacking UNC-6 or the UNC-5 receptor, thus they function in a parallel unknown pathway (Yee et al., 2011). Expression analyses in HeLa cells have determined that ENU-3 and one of its paralogs, C38D4.1 localize to the nuclear membrane/ER while another of its paralogs, K01G5.3 is an intracellular membrane-associated protein.

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Action potentials recorded from bundles of very thin, gray matter axons in rat cerebellar slices using a grease-gap method

Cited by 4 publications

References 33 publications

Typical gray matter axons in mammalian brain fail to conduct action potentials faithfully at fever-like temperatures

Typical gray matter axons in mammalian brain fail to conduct action potentials faithfully at fever-like temperatures

Components of action potential repolarization in cerebellar parallel fibres

Analysis of the ENU-3 protein family in nervous system development in C. elegans

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